1. Field of the Invention
The invention generally relates to the formation of materials for photovoltaic devices and more specifically to the synthesis of CsSnI3 by solution based method.
2. Description of the Prior Art
The current photovoltaic technologies can be classified by the different materials used for the light absorption in a solar cell. These materials include amorphous and polycrystalline silicon, CdTe, CuInxGa1-xSe2 (CIGS), GaAs, and photosensitive organic dyes. A transformative technology may emerge when a new and better material is discovered for photovoltaic applications.
CsSnI3 is a unique phase-change material that exhibits four polymorphs. The black polymorph of CsSnI3 could be obtained through a phase transition from the yellow polymorph CsSnI3 by increasing its temperature above 425 K. It was further demonstrated by differential thermal analysis and X-ray diffraction that during the cooling of the black CsSnI3 from 450 K, its ideal cubic Perovskite structure (B-α) deformed to a tetragonal structure (B-β) at 426 K, and became an orthorhombic structure (B-γ) below 351 K. [1] The CsSnI3 is unique in combining two generally contra-indicated properties, strong photoluminescence (PL) and high electrical conductivity. [2, 3]
A need still exists in the industry for developing synthesis methods for CsSnI3, especially in large scale. The successful implementation of these materials for various applications requires a detailed understanding of both their processing and materials properties.
At present, the synthesis of CsSnI3 can be divided into solid-phase sintering and solution based methods. The solid-phase sintering method needs vacuum and high temperature which means high production costs. [1] For solution based method, K. Shum and Z. Chen offered a simple way to synthesize CsSnI3, but the final product is not pure (U.S. Published Patent Application No. 2012/0306053). Here, we provide a simple solution based method to synthesize substantially pure CsSnI3.